A. Technical field
The present invention relates to an apparatus and a process for producing (meth)acrylic acid.
B. Background Art
It is a general industrial practice to produce (meth)acrylic acid by catalytic gas phase oxidation. However, (meth)acrylic acid is very easily polymerizable. Therefore there is a possibility that its polymerization often might occur in its production process and, as a result, it might become impossible to continue the operation.
Usually, polymerization inhibitors such as hydroquinone, phenothiazine, hydroquinone monomethyl ether, diphenylamine, copper dialkyldithiocarbamates, N-oxyl compounds and molecular-oxygen-containing gases are used in order to inhibit the polymerization of (meth)acrylic acid in its production process, or the inner wall surface of the apparatus is treated in order to prevent solid materials, such as polymers and deposits, from attaching to the apparatus.
However, even the use of the polymerization inhibitor or the inner wall surface treatment for the apparatus still results in insufficient inhibition of the polymerization of (meth)acrylic acid.